1. Field of the Invention
The present invention pertains to apparatus for distributing granular materials and the like over a defined pattern, and in particular pertains to such apparatus mounted to vehicles for traveling over relatively large land areas.
2. Description of the Prior Art
It is frequently desired to distribute materials over a relatively large land area. For example, the agricultural industry has had a longstanding need for efficiently distributing granular or pelletized fertilizers, herbicides or insecticides and the like over agricultural fields in which crops are grown. It is also desirable to sow seeds over the same area to establish the plantings. One of two major types of applicators in use today include an impeller-type rotor which utilizes centrifugal force to propel pelletized or granular material over a broadcast area. However, objectionable edge effects have been encountered where the spray pattern has been interrupted by the vehicle to which the applicator is attached. It has also been found that the materials have not been spread as uniformly as has been desired.
The second general type of applicator uses pneumatic energy or forced air to suspend and spray pelletized or granular materials or the like, rather than imparting a momentum thereto by a spinning rotor. In order to provide a more uniform spread of the material, particularly over large areas, it has been found advantageous to provide a multiple number of flow paths terminating in different points of discharge. One example of an applicator of this type is given in U.S. Pat. No. 4,562,968.
One problem associated with pneumatic spreaders is the pressure drop experienced within the distribution system, caused by fairly long path lengths which the materials must travel before their ultimate discharge in the desired pattern. In addition to long path lengths, multiple connection points of the conduits carrying materials along a particular flow path and the number of corners and crevices included in the flow path also impair the efficient operation of the overall system and frequently have been observed to lead to inconsistent distribution along different flow paths.
Improvements in distribution systems have focused upon reducing the complexity of the cooperating subsystems need to provide a reliable, reasonably uniform material distribution. However, further simplification is still required. In addition to contributing directly to capital investment costs, complex equipment increases the likelihood of breakdown resulting in costly downtime for an equipment user. In addition, it is important that repair parts be readily obtained as needed to reduce downtime and to facilitate regular maintenance of the equipment. If a large number of relatively complex parts are required, it is less likely that parts suppliers will maintain a full inventory of replacement parts, particularly where the supplier supports a number of different models of equipment.